Alkylamine-Templated Niccolite Frameworks of [GaIIIMII(HCOO)6] (M = Fe, Ni): Structure, Magnetism, and Dielectricity

The five heterometallic formate frameworks [EtA]­[GaIIIFeII(HCOO)6] (1; EtA = CH3CH2NH3+), [DMA]­[GaIIIFeII(HCOO)6] (2; DMA = (CH3)2NH2+), [DEtA]­[GaIIIFeII(HCOO)6] (3; DEtA = (CH3CH2)2NH2+), [MA]­[GaIIINiII(HCOO)6] (4; MA = CH3NH3+), and [DMA]­[GaIIINiII(HCOO)6] (5) were synthesized through solvothermal methods. Complexes 15 are isotructural, and all crystallize in the trigonal P1c space group. Each metal center is 6-connected, with each HCOO bridging ligand in an anti-anti mode to build a three-dimensional niccolite-like architecture. All of the complexes exhibit weak ferromagnetism at low temperature. A variable-temperature (VT) dielectric study indicates that the dielectric anomaly is induced by the freezing of motions from the protonated amines during the freezing process.